Heat dissipation fan

ABSTRACT

An exemplary heat dissipation fan includes a fan housing  10,  a bearing assembly  20 , a stator  30  and a rotor  40.  The fan housing includes a base  12  and a central tube  14  extending upwardly from the base. The bearing assembly includes a bearing  23  received in the central tube, a porous wick element  24  and a locking washer  25.  The stator is mounted around the central tube. The rotor includes a shaft  47  extending through a bearing hole  231  of the bearing. The locking washer is mounted around the shaft and fixed on a top end of the central tube. The locking washer, the bearing and the shaft cooperatively form an oil reservoir  50  in the top end of the central tube. The porous wick element is received in the oil reservoir and physically contacts with the bearing.

BACKGROUND

1. Technical Field

The present invention relates to a heat dissipation fan, and more particularly relates to a heat dissipation fan which has a good lubricating effect.

2. Description of Related Art

With the continuing development of the electronic technology, electronic packages such as CPUs (central processing units) are generating more and more heat that is required to be dissipated immediately. Heat dissipation fans are commonly used in combination with heat sinks for cooling CPUs. Performances of heat dissipation fans mostly depend on performances of bearings used in the heat dissipation fans. Good lubricating qualities of the bearings increase the life-span of the bearings.

A typical heat dissipation fan comprises a fan housing having a central tube extending upwardly therefrom, a bearing received in the central tube, a stator mounted around the central tube, and a rotor rotatable with respect to the stator. The rotor includes a hub and a shaft extending from the hub into the bearing. The central tube has an opening defined at a top end thereof. The bearing is inserted into the central tube through the opening. Lubricating oil is injected into the central tube to lubricate the bearing and the shaft. A lubricating effect of the bearing and the shaft can be properly maintained when the heat dissipation fan is vertically mounted. However, when the heat dissipation fan is mounted in an upside-down manner, the lubricating oil will leak out of the central tube through the opening of the central tube and the amount of the lubricating oil in the bearing is thus gradually reduced. The friction between the shaft and the bearing is therefore increased due to a decrease of the lubricating oil, which results in uncomfortable noise or malfunction being generated. As a result, the performance of the heat dissipation fan deteriorates, and the life-span of the fan is accordingly shortened.

What is needed, therefore, is a heat dissipation fan which can reduce or eliminate a leakage of the lubricant oil from the bearing thereof.

SUMMARY

The present invention relates to a heat dissipation fan. According to an embodiment of the present invention, the heat dissipation fan includes a fan housing, a bearing assembly, a stator and a rotor. The fan housing includes a base and a central tube extending upwardly from a top surface of the base. The bearing assembly includes a bearing received in the central tube and defining a bearing hole therein, a porous wick element and a locking washer. The stator is mounted around the central tube. The rotor includes a shaft extending through the bearing hole of the bearing. The locking washer is mounted around the shaft and fixed on a top end of the central tube. The locking washer, the bearing and the shaft cooperatively form an oil reservoir in the top end of the central tube. The porous wick element is received in the oil reservoir and physically contacts with the bearing.

Other advantages and novel features of the present invention will become more apparent from the following detailed description of preferred embodiment when taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 an assembled, isometric view showing a heat dissipation fan in accordance with an embodiment of the present invention.

FIG. 2 is an exploded, isometric view of the heat dissipation fan of FIG. 1.

FIG. 3 is a view similar to FIG. 2, but shown in an up-side-down aspect.

FIG. 4 is a cross-section view of the heat dissipation fan of FIG. 1, taken along line IV-IV thereof.

FIG. 5 is an enlarged view of a circled portion V of FIG. 4.

DETAILED DESCRIPTION OF THE EMBODIMENT

Reference will now be made to the drawings to describe the various present embodiments in detail.

Referring to FIGS. 1-3, a heat dissipation fan according to an embodiment includes a rotor 40, a stator 30 in respect to which the rotor 40 is rotatable, a fan housing 10 receiving the rotor 40 and the stator 30 therein, and a bearing assembly 20.

The fan housing 10 comprises a base 12 and a central tube 14 extending upwardly from a top surface of a central portion of the base 12. The central tube 14 defines a central hole 142 therein and forms an open end at a top portion thereof. An annular recess 144 is formed on an inner circumference of the top portion of the central tube 14. The annular recess 144 communicates with the central hole 142. The top portion of the central tube 14 has an inner diameter which is larger than that of the other portion of the central tube 14. A receiving concave 120 is formed on a bottom surface of the central portion of the base 12. The receiving concave 120 faces opposite to the central hole 142 of the central tube 14 and is isolated from the central hole 142 of the central tube 14 by the base 12. In other words, the receiving concave 120 is aligned with the central hole 142, but does not communicate with the central hole 142.

The stator 30 comprises a stator core 33 consisting of several layers of yokes, stator coils 35 wound around the stator core 33 to establish an alternating magnetic field, and a PCB (printed circuit board) 31 electrically connected with the stator coils 35. To avoid the coils 35 from electrically contacting with the stator core 33, upper and lower insulating frames 37 are used to cover the stator core 33 and electrically insulate the stator coils 35 from the stator core 33.

The rotor 40 comprises a hub 42 forming downwardly a shaft seat 46 at a central portion thereof, a plurality of fan blades 44 extending radially outwardly from an outer periphery of the hub 42, an annular magnet 45 adhered to an inner surface of the hub 42, and a shaft 47 retained in and extending downwardly from the shaft seat 46. The shaft 47 defines an annular slot 471 in a circular circumference thereof, at a position near a top end of the shaft 47 which locates adjacent to the hub 42. A cylindrical protrusion 48 extends downwardly from the hub 42, wherein the protrusion 48 surrounds and spaces a distance from the shaft seat 46. The protrusion 48 and the shaft seat 46 cooperatively define an annular chamber 480 therebetween.

The bearing assembly 20 comprises a wear pad 21, a bearing 23, a porous wick element 24, a locking washer 25 and a magnetic unit 27. The bearing 23 is a sleeve bearing and made from sintering powders such as copper powders or ceramic powders. A plurality of pores (not shown) are defined in the bearing 23 and communicate with each other. The bearing 23 is received in the central hole 142 of the central tube 14 via the open end of the central tube 14. The bearing 23 defines an axial hole 231 therein for extension of the shaft 47 therethrough. A circular cavity 232 is formed in a top portion of the bearing 23. The cavity 232 communicates with the axial hole 231. Thus, the top portion of the bearing 23 has an inner diameter which is larger than that of the other portion of the bearing 23. Two channels 234 are axially defined in an outer surface of the bearing 23. The channels 234 communicate with the axial hole 231 of the bearing 23 for guiding oil at the top portion of the bearing 23 to return back to a bottom portion of the bearing 23.

The porous wick element 24 is cylindrically-shaped in configuration. The porous wick element 24 is made of a porous material, such as polyurethane foam plastic, foamed metal or sponge. The porous wick element 24 is received in the cavity 232 of the bearing 23. More specifically, a bottom surface and an outer circumference surface of the porous wick element 24 are interferentially and physically respectively attached to a top surface and a side surface of the bearing 23 defining the cavity 232. A plurality of pores (not shown) are defined in the porous wick element 24 and communicate with each other.

The locking washer 25 is made of a material having high strength, high abrasion resistance and low friction factor, such as nylon. Referring to FIGS. 4-5, the locking washer 25 comprises a cylindrical mounting portion 251, a retaining ring 253 extending inwardly from a top end of the mounting portion 251, and a flange 255 extending upwardly and perpendicularly from a top surface of the retaining ring 253. The flange 255 offsets inwardly a distance with respect to the mounting portion 251. An inner diameter of the flange 255 is greater than an inner diameter of the retaining ring 253.

The mounting portion 251 has an outer diameter substantially equals to the diameter of the annular recess 144 of the central tube 14. The retaining ring 253 extends horizontally from the top end of the mounting portion 251 towards the slot 471 of the shaft 47, and substantially covers the open end of the central tube 14. The retaining ring 253 defines an inner hole 250 in a middle portion for extension of the shaft 47 therethrough. A diameter of the inner hole 250 of the retaining ring 253 is slightly larger than a diameter of an outer surface of the shaft 47 at the slot 471, but smaller than a diameter of the other portion of the shaft 47. Thus, the retaining ring 253 of the locking washer 25 is engaged in the slot 471 of the shaft 47 to limit an axial movement of the shaft 47. A narrow gap is defined between an inner circumferential surface of the retaining ring 253 and the outer surface of the shaft 47 defining the slot 471, in order to avoid an interference between the shaft 47 and the retaining ring 253 during rotation of the shaft 47. The flange 255 and the mounting portion 251 are staggered to each other, thereby forming a step 254 on the top surface of the retaining ring 253 above the mounting portion 251. In other words, the step 254 is formed between the mounting portion 251 and the flange 255. A diameter of the flange 255 is smaller than a diameter of the protrusion 48 of the hub 42. The flange 255 extends upwardly from the top surface of the retaining ring 253 into the annular chamber 480.

The wear pad 21 is made of high abrasion resistant material. The wear pad 21 is mounted in a bottom end of the central hole 142 of the central tube 14, for supporting a bottom end of the shaft 47.

The magnetic unit 27 comprises a magnetic yoke 273 and a columned magnet 271. The magnetic yoke 273 is cup-shaped, having a close end and an opposite open end. An axial cross-sectional view of the magnetic yoke 273 is “U” shaped. The magnetic yoke 273 encloses the magnet 271 therein, along with a top surface of the magnet 271 exposed out of the magnetic yoke 273. Bottom surface and side surface of the magnet 271 are affixed to an inner surface of the magnetic yoke 273 to connect the magnet 271 and the magnetic yoke 273 together.

When assembled, the bearing 23 is mounted into the central tube 14, and the shaft 47 is rotatably received in the bearing 23. The porous wick element 24 is received in the cavity 232 of the bearing 23. The mounting portion 251 is pressingly fitted in the annular recess 144 of the central tube 14. The top portion of the central tube 14 is bent inwardly to form a pressing portion 145 abutting on the step 254 of the retaining ring 253 for keeping the locking washer 25 and the bearing 23 in the central tube 14. The retaining ring 253 of the locking washer 25, the bearing 23 and the shaft 47 cooperatively form an oil reservoir 50 at the top portion of the bearing 23. The porous wick element 24 is received in the oil reservoir 50. The magnet 271 and the magnetic yoke 273 are both received in the receiving concave 120 of the base 12 of the fan housing 10, wherein the top surface of the magnet 271 faces to the bottom end of the shaft 47.

During operation, the rotor 40 is driven to rotate by the interaction between the alternating magnetic field established by the coils 35 of the stator 30 and the magnet 45 of the rotor 40. The lubricating oil creeps up along the rotating shaft 47 under the influence of the centrifugal force generated by the rotation of the shaft 47 and then escapes to the oil reservoir 50 through a clearance defined between the top end of the bearing 23 and the shaft 47. The slot 471 of the shaft 47 prevents the oil from continuously creeping up along the shaft 47. Since the oil reservoir 50 is almost hermetically sealed by the retaining ring 253, the retaining ring 253 can prevent the lubricating oil from leaking out of the oil receiver 50.

As the porous wick element 24 defines a plurality of pores therein, the porous wick element 24 can absorb the lubricating oil accumulated in the oil receiver 50, thereby further preventing the lubricating oil from leaking out of the oil receiver 50. The porous wick element 24 then returns the lubricating oil back to the bearing 23 under a capillary force generated by the pores of the bearing 23. The porous wick element 24 can absorb the lubricating oil in the oil reservoir 50 and prevent the lubricating oil from leaking out of oil reservoir 50 whether the heat dissipation fan is positioned in a top side up manner, a lain down manner, or an upside-down manner according to requirements. Preferably, the pores defined in the porous wick element 24 have an average pore size lager than that of the pores defined in the bearing 23, which makes the bearing 23 generate a larger capillary force than the porous wick element 24 to accelerate the lubricating oil flowing back to the bearing 23 from the porous wick element 24. Thus, the lubricating oil is kept from leaking out of the bearing 23. Good lubrication of the bearing 23 and the shaft 47 is thus consistently maintained, thereby improving the quality and life-span of the heat dissipation fan.

Moreover, the flange 255 of the locking washer 25 can further prevent the lubricating oil from leaking out of the oil reservoir 50. The bottom surface and the side surface of the magnet 271 are covered by the magnetic yoke 273, which prevents magnetic energy from leaking out from the magnetic yoke 273. Thus, the magnet 271 can generate a magnetic attraction force which attracts the shaft 47 to always maintain in contact with the wear pad 21 and prevents the shaft 47 from floating along an axial direction of the bearing 23. The axially upward movement of possible floating of the rotor 40 during operation of the heat dissipation fan is avoided, whereby the rotor 40 is maintained to rotate steadily.

It is to be understood, however, that even though numerous characteristics and advantages of the present invention have been set forth in the foregoing description, together with details of the structure and function of the embodiments, the disclosure is illustrative only, and changes may be made in detail, especially in matters of shape, size, and arrangement of parts within the principles of the invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed. 

1. A heat dissipation fan comprising: a fan housing comprising a base and a central tube extending upwardly from a top surface of the base; a bearing assembly comprising a bearing, a porous wick element and a locking washer, the bearing being received in the central tube and defining a bearing hole therein; a stator mounted around the central tube; and a rotor comprising a shaft extending through the bearing hole of the bearing, the locking washer being mounted around the shaft and fixed on a top end of the central tube, wherein the locking washer, the bearing and the shaft cooperatively define an oil reservoir in the top end of the central tube, and the porous wick element is received in the oil reservoir and physically contacts with the bearing.
 2. The heat dissipation fan of claim 1, wherein the locking washer comprises a retaining ring extending from the top end of the central tube towards an outer surface of the shaft.
 3. The heat dissipation fan of claim 2, wherein the locking washer further comprises a cylindrical mounting portion, the retaining ring extending inwardly from a top of the mounting portion towards the shaft, an annular recess defined in a top portion of the central tube for mounting the mounting portion of the locking washer therein.
 4. The heat dissipation fan of claim 3, wherein the locking washer further comprises a cylindrical flange extending upwardly from a top surface of the retaining ring, the flange and the mounting portion being staggered to each other with a step formed on the top surface of the retaining ring above the mounting portion, a top of the central tube bended inwardly to form a pressing portion to press on the step for keeping the locking washer and the bearing in the central tube.
 5. The heat dissipation fan of claim 4, wherein the rotor further comprises a hub, the hub forming a shaft seat fixing one end of the shaft and a cylindrical protrusion extending downwardly from the hub around the shaft seat, a diameter of the flange being smaller than a diameter of the protrusion, the flange extending from the retaining ring into a chamber defined between the shaft seat and the protrusion.
 6. The heat dissipation fan of claim 2, wherein the shaft defines an annular slot in a circumference thereof, at a position corresponding to the locking washer, the retaining ring extending from the central tube into the slot.
 7. The heat dissipation fan of claim 1, wherein the porous wick element is made of a porous material and defines a plurality of pores therein.
 8. The heat dissipation fan of claim 7, wherein the bearing defines a circular cavity in a top portion thereof, the porous wick element being received in the cavity, a bottom surface and an outer side surface of the porous wick element being physically attached to a top surface and a side surface of the bearing defining the circular cavity, respectively.
 9. The heat dissipation fan of claim 7, wherein the bearing is an oil-impregnated sleeve bearing and defines a plurality of pores therein.
 10. The heat dissipation fan of claim 9, wherein the pores defined in the porous wick element have an average pore size lager than that of the pores defined in the bearing.
 11. The heat dissipation fan of claim 1, wherein the bearing assembly further comprises a magnetic unit, the magnetic unit comprising a magnet, the base of the fan housing defining a receiving concave on a bottom surface, the central tube defining a central hole for receiving the bearing therein, the receiving concave facing opposite to and being isolated from the central hole of the central tube, the magnet being received in the receiving concave.
 12. The heat dissipation fan of claim 11, wherein the magnetic unit further comprises a cup-shaped magnetic yoke enclosing the magnet therein, and a top surface of the magnet is exposed out of the magnetic yoke and faces toward a bottom of the shaft.
 13. A heat dissipation fan comprising: a fan housing comprising a base and a central tube extending upwardly from a center of the base; a bearing received in the central tube and defining a bearing hole therein; a stator mounted around the central tube; a rotor comprising a shaft extending through the bearing hole of the bearing, an oil reservoir being defined in the central tube near a top end of the central tube; and a porous wick element received in the oil reservoir and physically contacting with a top end of the bearing.
 14. The heat dissipation fan of claim 13, further comprising a locking washer mounted to the top end of the central tube, the locking washer including a retaining ring extending from the central tube towards the shaft, the oil reservoir being defined among the retaining ring, the bearing and the shaft.
 15. The heat dissipation fan of claim 14, wherein the bearing defines a cavity in a top end thereof, the porous wick element being received in the cavity, a bottom surface and an outer side surface of the porous wick element being physically attached to the bearing. 